This paper proposes a strengthened RIME algorithm to tackle continuous optimization problems. RIME is a newly proposed physical-based evolutionary algorithm (EA) inspired by the soft and hard rime ...growth process of rime-ice, which has a powerful exploitation ability. But in complex optimization problems, RIME will easily trap into local optima and the optimization will become stagnation. Noticing this issue, we introduce three techniques to the original RIME: (1) Latin hypercube sampling replaces the random generator as the initialization strategy, (2) modified hard rime search strategy, and (3) embedded distance-based selection mechanism. We evaluate our proposed SRIME in 10-D, 30-D, 50-D, and 100-D CEC2020 benchmark functions and eight real-world engineering optimization problems with nine state-of-the-art EAs. Experimental and statistical results show that the introduction of three techniques can significantly accelerate the optimization of the RIME algorithm, and SRIME is a competitive optimization technique in real-world applications. Ablation experiments are also provided to analyze our proposed three techniques independently, and the embedded distance-based selection contributes most to the improvement of SRIME. The source code of SRIME can be found in
https://github.com/RuiZhong961230/SRIME
.
There have been great concerns on poor visibility and hazardous issues due to fogging and ice/frost formation on glass surfaces of windshields, windows of vehicles/airplanes, and solar panels. ...Existing methods for their monitoring and removal include those active ones (such as using resistance heating) or passive ones (such as using surface icephobic treatments), which are not always applicable, effective or reliable. In this study, we proposed a novel strategy by implementing transparent thin film surface acoustic wave (SAW) devices by directly coating ZnO films onto glass substrate and studied their de-fogging, active anti-icing and de-icing mechanisms using the SAW technology. Effects of powers and wavelengths of SAW devices were investigated and influences of acousto-heating and surface hydrophobic treatments were evaluated. Results showed that de-fogging time was dramatically decreased with the increase of SAW powers when the thin film-based SAW devices were exposed to humid air flow for different durations. The icing accretion was significantly delayed under the applied SAW agitation, and SAW application has also effectively promoted de-icing on glass substrate, due to the interfacial nanoscale vibration and localized heating effect.
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•An active technique of anti-fogging and ice mitigating platform on glass was proposed.•Effective de-fogging was achieved using SAW devices with different powers.•Anti-icing and de-icing performances were achieved with surface hydrophobic treatments.•Nanoscale surface vibration and acousto-thermal effect are the key mechanisms.
•The effects of porous surfaces on hydrate nucleation and growth were evaluated.•Surface defects and inner pore convection give rise to numerous nucleation sites.•Hydrate nucleating in inner pore ...grows into hydrate fibers.•Porous surfaces enhance hydrate dissolution and Ostwald ripening.•Hydrate dissolution/re-growth cycles on porous surfaces were observed.
Porous media were reported to significantly enhance hydrate nucleation and growth kinetics due to abundant specific surface area and pore texture, but the mechanisms behind the promotion remain an open topic, and little is known with respect to hydrate morphologies on porous surface. In this work, we investigated hydrate formation loaded by activated carbon (AC), and the influence of porous surfaces on hydrate nucleation and growth was evaluated. Three hydrate morphologies of rime-like hydrates, hydrate fibers and hydrate chunks appear in turn, which form at surface bulges, inner pores and interstitial pores, respectively. Surface micro bulges and two-way convection in inner pores increase gas–liquid contact area at micro scale and provide numerous potential nucleation sites, so fast hydrate nucleation is anticipated. The induction time is less than 30 min for 52.17% of the experiments, while no induction period was observed for 28.26% of the experiments. Since hydrate fibers grow out form inner pores, their diameter depends on pore size, the average diameter and median diameter of them are 178.25 μm and 147.89 μm separately, and more hydrate fibers were observed under milder conditions, which is completely different from that in bulk water systems. Hydrate dissolution and Ostwald ripening at stable hydrate regimes occur, which is significantly enhanced by porous surfaces, giving rise to hydrate dissolution/re-growth cycles. These findings would shed light on the understanding of hydrate nucleation and growth on porous surfaces.
The data produced by the new generation of interferometers are affected by a wide variety of partially unknown complex effects such as pointing errors, phased array beams, ionosphere, troposphere, ...Faraday rotation, or clock drifts. Most algorithms addressing direction-dependent calibration solve for the effective Jones matrices, and cannot constrain the underlying physical quantities of the radio interferometry measurement equation (RIME). A related difficulty is that they lack robustness in the presence of low signal-to-noise ratios, and when solving for moderate to large numbers of parameters they can be subject to ill-conditioning. These effects can have dramatic consequences in the image plane such as source or even thermal noise suppression. The advantage of solvers directly estimating the physical terms appearing in the RIME is that they can potentially reduce the number of free parameters by orders of magnitudes while dramatically increasing the size of usable data, thereby improving conditioning. We present here a new calibration scheme based on a nonlinear version of the Kalman filter that aims at estimating the physical terms appearing in the RIME. We enrich the filter’s structure with a tunable data representation model, together with an augmented measurement model for regularization. Using simulations we show that it can properly estimate the physical effects appearing in the RIME. We found that this approach is particularly useful in the most extreme cases such as when ionospheric and clock effects are simultaneously present. Combined with the ability to provide prior knowledge on the expected structure of the physical instrumental effects (expected physical state and dynamics), we obtain a fairly computationally cheap algorithm that we believe to be robust, especially in low signal-to-noise regimes. Potentially, the use of filters and other similar methods can represent an improvement for calibration in radio interferometry, under the condition that the effects corrupting visibilities are understood and analytically stable. Recursive algorithms are particularly well adapted for pre-calibration and sky model estimate in a streaming way. This may be useful for the SKA-type instruments that produce huge amounts of data that have to be calibrated before being averaged.
Il ladro di Servagno Marco Grimaldi
Carte romanze,
12/2020, Letnik:
8, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Il contributo analizza le fonti romanze relative a un personaggio di nome Salvain, Selvain o Servein, in italiano Salvagno, e propone una congettura per il v. 14 del sonetto di Dante Ben ti faranno ...il nodo Salamone.
•Dynamic icing processes on rotating aero-engine spinners were investigated.•Ice accretion processes on three commonly-used aero-engine spinners were compared.•Growth of the rime ice layers accreted ...over the spinner surfaces were characterized.•Detrimental effects of the ice accretion over the spinner surface were evaluated.
An experimental study was conducted to investigate the dynamic ice accretion process over the surfaces of rotating aero-engine spinners and to examine the detriment effects of the ice accretion on the airflow to be inhaled by aero-engines. Three scaled spinner-fan models with different spinner shapes (i.e., conical-shaped, coniptical-shaped, and elliptical-shaped spinners) were manufactured and exposed under typical rime and glaze icing conditions for a comparative study. During the experiments, while a high-speed imaging system was used to record the dynamic ice accretion process over the rotating spinner models, a high-resolution particle image velocimetry (PIV) system was utilized to examine the trajectories of super-cooled water droplets as they approach to the surfaces of the spinner models. It was found that, under typical rime conditions, while accreted ice layers were found to conform well with the original shapes of the spinner models in general, the total amount of the ice mass accreted over the spinner surfaces were found to be a strong dependent on the spinner shapes. While the conical-shaped spinner was found to have the largest amount of ice accretion (i.e., 60–80% more than those over the other two spinner models) over almost entire spinner surface, ice accretion was found to take place mainly in the front portion of the coniptical-shaped and elliptical-shaped spinners. Under the glaze icing condition, in addition to forming ice layers over the spinner surfaces, very complicated, needle-shaped icicles were also found to grow rapidly out from the spinner surfaces and extrude into the incoming airflow, due to the effects of the centrifugal forces associated with the rotation motion. The complex glaze ice structures accreted over the spinner surface were found to induce significant disturbances/distortions and even cause large-scale flow separations for the airflow near the iced spinner surfaces, which would significantly degrade the quality of the inlet airflow to be inhaled by aero-engines, thereby, adversely affecting the performance of aero-engines.
•Sobol initialization, local optimal avoidance strategy and cross strategy are introduced into the original RIME.•The proposed SLCRIME is compared with the popular algorithms and variants to verify ...its performance.•SLCRIME-based multi-threshold image segmentation model is applied for COVID-19 X-ray images segmentation.•The proposed segmentation model has shown superior performance than other peers.
Image segmentation is a crucial technique in analyzing X-ray medical images as it aids in uncovering relevant information concealed within a patient's body, a pivotal aspect of the diagnostic process. The effectiveness of computer-aided diagnosis systems largely depends on the accuracy of the image processing methods. In recent years, multi-threshold image segmentation methods have found widespread application in medical image analysis. Despite the effectiveness of some renowned methods for binary threshold segmentation, the field still faces challenges due to the high cost of threshold computation. Metaheuristic algorithms hold the potential to address this issue as they can produce sufficiently reasonable solutions with manageable computational overheads. While some similar methods have been proposed, the imbalance between exploration and exploitation results in instability as the number of thresholds increases. Consequently, these solutions suffer from reduced efficiency in computing thresholds. In this study, a variant of the latest RIME algorithm, termed SLCRIME, is proposed. This paper replaces the pseudo-random method with low-discrepancy Sobol sequences for solution initialization. Additionally, two methods aimed at avoiding local optima and promoting information exchange within the solution set are introduced, further enhancing its capability to search for optimal threshold sets for IS systems. Subsequently, a multi-threshold image segmentation model based on SLCRIME is proposed and applied to segment 6 COVID-19 X-ray images. In the experiments, SLCRIME is compared with 6 peer algorithms, and the results are evaluated using image segmentation accuracy, feature similarity index metrics (FSIM), peak signal-to-noise ratio (PSNR), and structural similarity index metrics (SSIM). The analysis indicates that SLCRIME achieves optimal thresholds at reasonable computational costs and outperforms other algorithms in terms of performance.
During three winter seasons (2009–2011), Pb concentrations were measured in precipitation at 10 high-elevation sites in the Czech Republic, close to the borders with Austria, Germany, Poland, and ...Slovakia. Soluble and insoluble Pb forms were quantified in snow (vertical deposition), and rime (horizontal deposition). The objective was to compare Pb input fluxes into ecosystems via vertical and horizontal deposition, and to identify the residual Pb pollution sources in an era of rapidly decreasing industrial pollution. Lead soluble in diluted HNO3 made up 96% of total Pb deposition, with the remaining 4% Pb bound mainly in silicates. Three times higher concentrations of soluble Pb in rime than in snow, and 2.5 times higher concentrations of insoluble Pb in rime than in snow were associated with slightly different Pb isotope ratios. On average, the 206Pb/207Pb ratios in rime were higher than those in snow. Higher mean 206Pb/207Pb ratios of insoluble Pb (1.175) than in soluble Pb (1.165) may indicate an increasing role of geogenic Pb in recent atmospheric deposition. A distinct reversal to more radiogenic 206Pb/207Pb ratios in snow and rime in 2010, compared to literature data from rain-fed Sphagnum peatlands (1800–2000 A.D.), documented a recent decrease in anthropogenic Pb in the atmosphere of Central Europe. Since the early 1980s, Pb concentrations in snow decreased 18 times in the rural south of the Czech Republic, but only twice in the industrial north of the Czech Republic. Isotope signatures indicated that Pb in today's atmospheric deposition is mainly derived from Mesozoic ores mined/processed in Poland and coal combustion in the Czech Republic and Poland.
•Pb concentration in rime is 3 times higher than in snow, showing a different origin.•Today, Pb in deposition is more radiogenic than Pb buried in peat around 1800AD.•206Pb/207Pb in the insoluble Pb fraction is higher than in the soluble fraction.•Since 1983, Pb deposition in rural areas decreased 18 times.•Over the same period of time, Pb deposition in industrial areas decreased only twice.
•Combining rigid sphere model and computational fluid dynamics for rime ice simulation.•Model based on first principles with little physical modeling.•Usage of Cartesian grid and its tree data for ...reducing overall computational cost.•Demonstrated the feasibility of 3D calculations using rigid sphere model.•Fair agreement with experiment and other simulations in 2D and 3D calculations.
A 2D/3D numerical model for rime ice shape prediction is developed by combining the rigid sphere model (RSM) and computational fluid dynamics (CFD), and its characteristics are investigated. In the RSM, the ice accretion is modeled based on first principles with little physical modeling. The ice particle on an airfoil is described as a rigid sphere, and the ice shape is represented as a collection of rigid spheres. We use a non-body-fitted hierarchical Cartesian grid-based CFD solver so that complex ice shape represented by RSM can be handled. The tree data of the hierarchical Cartesian grid is also used for fast search of droplet positions. In addition, multiple ice particles are modeled as one large particle to reduce the number of trajectory calculations. The sensitivity of several parameters in the calculation is studied in 2D. Subsequently, 3D ice accretion analysis on NACA0012 airfoil using the RSM is performed for the first time. The simulation results are compared with those of the wind-tunnel experiments conducted at NASA. Although the RSM is a simple ice accretion model, reliable results are obtained in both 2D and 3D calculations.
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